Prediction of Mechanical Behavior of Equivalent Adhesive-Layer Using Theory of Duality of Famage

Concepts of equivalent adhesive-layer and Theory of Duality of Damage (TDD) are presented. Basic idea of the TDD is to assume that material damaged consists of two parts, i.e., Relative Non-Damaged Part (RNDP) and Complete Damaged Part (CDP). The mechanical behaviors of the material damaged can be simulated simultaneously by both mechanical behaviors of the RNDP and the CDP. The RNDP can be simulated by linear-elasticity and non-linear elasticity, respectively. The CDP can be approximately determined in engineering significant. Observed stress-strain relation of the equivalent adhesive layer of a steel/steel butt joint is measured. Evolution equation of damage of the equivalent adhesive-layer is established, and increment equation of stress-strain including effect of damage is given. The observed stress-strain relation is predicted through four damage parameters, i.e., plastic strain trajectory, plastic strain energy density, total strain trajectory, and total strain energy density. As a result, it is shown that the stress-strain curves predicted are of consistence with the observed stress-strain curve. The result predicted using total strain trajectory is better than others. It should be pointed out that the method presented in this paper could be applied to a variety of damaged structures not only to the equivalent adhesive-layer.